This invention relates to the field of data communication using a frame relay network, and more particularly, to an automatic configuration system and method for configuring time slots dedicated to data communication over a frame relay network. Although not limited to this particular application, the automatic configuration system and method are particularly suited for implementation in a digital service unit (DSU).
Modern communications networks often include a number of paths or links that are interconnected to route information such as voice, video, or data traffic from one location of the network to another. At each location, an interconnect node couples a plurality of source nodes and destination nodes to the network. In some cases, the sources and destinations are incorporated in a private line network that may include a series of offices connected together by leased-lines with switching facilities and transmission equipment owned and operated by the carrier or service provider and leased to the user. This type of network is conventionally referred to as a xe2x80x9ccircuit-switching network.xe2x80x9d Accordingly, a source node of one office at one location of the network may transmit data to a destination node of a second office located at another location of the network through their respective switching facilities.
At any given location, a large number of source nodes may desire to communicate through their respective switching facilities, or interconnect node, to destination nodes at various other locations of the network. The data traffic from the various source nodes is first multiplexed through the source switching facility, then demultiplexed at the destination switching facility and finally delivered to the proper destination node. A variety of techniques for efficiently multiplexing data from multiple source nodes onto a single circuit of the network are presently employed in private line networks. For instance, time division multiplexing (xe2x80x9cTDMxe2x80x9d) affords each source node full access to the allotted bandwidth of the circuit for a small amount of time. The circuit is divided into defined time segments, with each segment corresponding to a specific source node, to provide for the transfer of data from those source nodes, when called upon, through the network.
Frame-relay networks, on the other hand, are often referred to as xe2x80x9cpacket-switching networks.xe2x80x9d Packet-switching networks, as opposed to circuit-switching networks, allow multiple users to share data network facilities and bandwidth rather than providing a specific amount of dedicated bandwidth to each user, as in TDM. Instead, packet switches divide bandwidth into connectionless, virtual circuits. As is known, virtual circuit bandwidth is consumed only when data is actually transmitted. Otherwise, the bandwidth is not used. In this way, packet-switching networks essentially mirror the operation of a statistical multiplexer (whereby multiple logical users share a single network access circuit).
It is often the case that a time division multiplexing (TDM) connection line is employed to interface between a source node and an interconnect node in a frame relay network. This may be accomplished by establishing a TDM connection between the customer premises and the frame relay network, such as a T1 line, which is known to those skilled in the art, having a number of time slots for both data and voice communications. Of the time slots that are available, one or more may be dedicated to frame relay traffic by the service provider. Thus the end user is required to configure their frame relay equipment to communicate using these dedicated time slots.
Configuration of a frame relay device which interfaces with a frame relay network using a TDM connection line is a manual process that can be a tedious and error prone task. Generally, in such situations, the user or the service provider configures the exact time slots on the TDM connection line that have been dedicated to carry frame relay traffic to the frame relay device. To do so, the user or service provider needs to know the time slots which have been so dedicated. Also, the user or service provider needs to identify the local management interface used by the frame relay components in this network.
The performance of these tasks can be costly. For instance, the seller of the frame relay digital service units (DSU""s) to the end user may be required to visit the customer premises to configure the network at start-up. A DSU is generally a unit which provides data terminal equipment with access to a local loop. Also, in the case where a TDM connection line is already employed, it is possible that additional time slots may be added by the service provider, requiring a reconfiguration of the time slots employed for frame relay traffic resulting in further visits. In the case where customers employ many DSU""s in their organization, the cost of configuration of these networks may be significant.
Consequently, there is a need for a system and method for configuring a frame relay network in an economic and efficient manner to reduce the cost and inconvenience of installing and updating frame relay service to an end user.
The present invention provides an automatic configuration system and method for automatically configuring a frame relay network by the automated determination of the time slots on a TDM connection line and the automated determination of the type of local management interface employed by the frame relay device employed by the service provider.
According to the automatic configuration system of the preferred embodiment of the present invention, a frame relay DSU employs a processor which operates pursuant to operating logic stored on a memory. The operating logic includes logic which automatically determines the time slots that are dedicated for frame relay service. In accomplishing this task, this logic samples the TDM line and detects high-level data link control (HDLC) flags transmitted by the frame relay device on any of the time slots. Next, the logic sets a level of confidence that corresponds to the probability that the HDLC flags detected were generated by the service provider""s frame relay device rather than being a random value. The logic then either increases or decreases the level of confidence based upon subsequent re-sampling of the TDM line which reveals changes or a lack of change in the HDLC flags detected previously on the various time slots. Once the level of confidence is sufficiently high, the time slots with the HDLC flags are deemed to have been dedicated for frame relay traffic. At this point, the logic attempts to establish a local management interface (LMI) with the service provider""s frame relay device using the dedicated time slots detected. The logic further examines multiple HDLC flags which emanate from different frame relay devices which communicate via the same TDM line, establishing specific LMI""s for each frame relay device.
The present invention may also be viewed as providing a method for automatically configuring a frame relay network by performing the steps in which the time slots dedicated for frame relay traffic are determined automatically. This method includes the steps of sampling the TDM line and detecting a high-level data link control (HDLC) flag on any time slot. Next, the step is executed of setting a level of confidence that corresponds to the probability that the HDLC flags detected were generated by a frame relay device from the service provider rather than being a random value. Thereafter, the steps of increasing or decreasing the level of confidence based on changes or a lack of change of the HDLC flags previously detected by subsequent re-sampling of the TDM line. Finally, once the level of confidence is sufficiently high, the time slots having the HDLC flags are assumed to be dedicated for frame relay traffic. The present method then executes the step of establishing the local management interface with the service provider""s frame relay device using the dedicated time slots. The logic further includes the step of examining the TDM line for multiple HDLC flags which emanate from different frame relay devices which communicate via the same TDM line.
Other features and advantages of the present invention will become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional features and advantages be included herein within the scope of the present invention, as defined by the claims.